Cause of Constant Low Potassium

[drewyreef]

I lost a few corals recently so sent off an ICP test. Amongst others it came back showing a huge lack of potassium. I dutifully dosed the recommended amounts as recommended and thought all was well as the tank recovered and looked good.

3rd October 2020

A month later I sent another one off and found another reading for low potassium

4th November 2020

I decided not to take a chance anymore and decided to put another one in 2 weeks later and again the potassium was low.

18th November 2020

From what I've read potassium should be reducing at a much lower rate than it is so I'm at a loss for what could be causing it. My other parameters are normal and the tank is over two years old so well established.

 

[Reefer5640]

Following

 

[TexasTodd]

Same bottle of supplement for all test times?
What do you feed?

 

[drewyreef]

Yep, the same supplements throughout. I buy 5 litres at a time to try and keep consistency.

I feed 2 cubes of frozen food and 10ml of Red Sea AB+ once a day.

 

[TexasTodd]

I'd maybe buy a small bottle and try just in case that one 5 liter is off on concentration possibly?
I think Randy advocated in the past to feed frozen and not rinse it as that also adds potassium but sounds like you have the covered and seems like it would be minor compared to the Triton stuff anyway.

 

[Righteous]

Do you by chance have a large refugium with lots of macro algae. That’s going to consume a lot of potassium on a regular basis.

I personally need to dose 10ml triton potassium supplement every week to maintain levels. It’s a 100g tank with triton recommended size fuge, so about 15g.

 

[Casket_Case]

To bring your potassium up throw a banana in there

 

[drewyreef]

@Righteous My refugium is 20l, about 8-9% of the overall system volume which is less than Triton recommend.

My cheato grows really fast so could that be sucking the potassium out of the water? Would cutting down the on time for the fuge lights help?

 

[TexasTodd]

I wouldn't adjust your ref, I'd add more potassium.

 

[Righteous]

Yes it definitely will use a lot of potassium. It’s why most fertilizers are made up of N-P-K. The refugium does a great job at reducing the N (nitrogen/nitrates) and P (phosphorus) in our tanks, but the K (potassium) can be limiting.

So it depends on how effective your refugium is and if it’s doing what you want. Reducing the lighting might mean your nitrates and phosphates go up... so if you try that then keep on top of checking those parameters, and looking at general health of tank.

Personally I look at a fast growing and healthy refugium as a great place for not only nutrient export, but pod diversity, reducing DOCs the skimmer misses, pH stabilizer (lights on at night), maybe some heavy metal abosoption, etc. So for me dosing potassium to keep it healthy is worth it.

 

[drewyreef]

Thanks for the info @Righteous. I think I'll stick to regular ICP testing and potassium dosing.

I should eventually be able to work out a small daily maintenance dose rather than large doses over a week or so

 

[Righteous]

Another question is what are you feeding? Some foods will supply more K. I believe unrinsed frozen food is often a good source.

Also to think of it, carbon dosing (like vinegar or nopox) along with skimming could use K up quicker... potassium gets used to by the bacteria and then skimmed out. So if you’re carbon dosing that could exacerbate it.